Hesham Eraqi - 10 months ago 58

Python Question

Let Y be a list of 100 ndarrays, such that Y[i] is an ndarray of an image, its shape is 160x320x3.

I want X no be an ndarrays that contains all the images, I do as follows:

`x = [ y[i] for i in range(0,10) ]`

But it produces a list of of 100 160X320X3 ndarrays. How can I modify it to get an ndarray of shape 100x160x320x3 ?

Answer Source

Calling `np.array`

on `Y`

(i.e `np.array(Y)`

) should turn the list of ndarrays into one ndarray, with the size of the first axis corresponding to the length of the list.

*Demo*:

```
>>> x = np.array([[1,2], [3,4]])
>>> c = [x,x] # list of 2x2 arrays
>>> c
[array([[1, 2],
[3, 4]]),
array([[1, 2],
[3, 4]])]
>>> np.array(c) # 2x2x2 array
array([[[1, 2],
[3, 4]],
[[1, 2],
[3, 4]]])
```

Just call `np.array`

on `Y`

, or `x`

if you only want a slice of `Y`

.